Four investigators having diverse research interests, but a common need for a transmission electron microscope, request a Philips 410. Their areas of research encompass: 1) The mechanism of action of taxol and its effect on microtubule assembly, stability, and regulation in both a macrophage-like cultured cell (J774.2) and a cell-free system; 2) The alteration of the plasma membrane of the luminal (urinary) cell by antidiuretic hormone (ADH), with particular reference to those structural changes affecting permeability; 3) The extra-cellular matrix of cardiac muscle cells will be examined to elucidate the physiological significance and interaction between the various macromolecules (e.g. collagen fibrils, elastin, fibronectin, microthreads, and the glycoproteins and glycosaminoglycans of the cell coat); 4) The proteins involved in the replication of procaryotic and eucaryotic viral DNAs. These studies will focus specifically on the proteins involved in the replication of adenovirus DNA in Ad-infected HeLa cells. Ultrastructural aspects of the replication of 0X RF1 DNA and the associated proteins will also be examined.